This could be where Mrs. Palin comes in. She’d be much more believable selling “border security first” to voters because she’s more likely to actually believe it. But if the Republican ticket does win, Vice President Palin will have a decision to make next year, when Mr. McCain will again try to push through a massive amnesty, whether the border is secure or not. The White House will be tempted to exploit her credibility with the right to try to sell amnesty to conservatives. But given the unprecedented outpouring of opposition to last year’s amnesty bill, it would be a serious mistake for her to agree to such a role, as it would undermine her own political viability in the future. Grass-roots enthusiasm about, say, a Palin-Jindal ticket in 2012 would be significantly dampened if she were to vigorously push the position that has caused Mr. McCain the greatest problems within his own party.

Barring a political blunder like this on her part, we probably won’t learn Mrs. Palin’s real views on immigration until she comes out from Mr. McCain’s shadow, either after his loss in November or when she runs to succeed him.